In an apparatus for the automatic removal of roving residues from roving-bobbin tubes, a sensor can detect a roving residue on tubes returned from the spinning frames and an automatic device can be triggered for removing those residues at least to a significant extent. In many cases, however, the automatic removal of the roving residue itself is incomplete and at least some of the roving-bobbin tubes will retain traces of rovings, i.e. residual roving.
So that a succession of empty roving-bobbin tubes can be returned to the roving frame or frames completely free from traces of the rovings, the traces are detected and roving-bobbin tubes which are empty, i.e. completely free from a roving residue, can be drawn from a magazine containing a store of such tubes and substituted for those tubes which have been incompletely stripped of the roving residues. For this purpose, the sensor downstream of the stripping device cooperates with a control unit which actuates a change mechanism and withdraws the empty tube from the magazine and substitutes it for the tube which still carries at least traces of the rovings.
It is known to color code such tubes as well so that rovings of different types are wound on tubes of a respective color and, as a consequence, it is important that color correspondence be maintained, i.e. that the tubes which are fed in each succession be of corresponding color.
In a standard yarn-producing operation, the full roving bobbins are supplied to a spinning machine or frame, e.g. a ring-spinning frame and when the roving runs out or there is a roving breakage, replacement of a roving-bobbin tube usually carrying turns of residual roving by a full roving bobbin can be automatically effected. This doffing operation results in a succession of roving-bobbin tubes having various amounts of residual roving thereon. This is the case because the bobbin-change operation is usually carried out before the roving is fully unwound from the bobbin, thereby ensuring that the spinning stations will not operate without a continuous supply of the roving. The residual roving on such tubes can range from several turns of the roving to several layers of such turns. Before such "empty" tubes are mounted on the spindles of the roving frame, these roving residues must be removed.
For this purpose, apparatus has been provided heretofore in a variety of forms. Reference may be had to the international patent classification Class B65H 73/00 covering such devices. Such devices for the removal of roving residue are referred to also as cleaning devices. They can remove the residue by suction, by flushing them off, by brushing them off or by stripping them from the tube in some other manner as long as the removal takes place without damage to the roving-bobbin tube.
Sensors for the detection of roving residue can also be of a wide variety of types. They can be optoelectronic and can cooperate with reflective foil on the sleeves; they can be of a video-type utilizing an image detected by the sensor. The sensor should have a range which covers the portion of the tube most likely to carry the residue and hence the capture strip which is provided on such a tube to engage or grip the roving. Such a capture strip may be composed of burrs or projections adapted to grip the roving as a leading end of the roving approaches the roving tube in the winding of the roving on the empty tube.
Depending upon the construction of the cleaning unit and its efficiency of operation, traces of the roving residue can remain on the roving-bobbin tubes. In other words, up to now it has not been possible to remove all of the residue completely or so perfectly that every tube following the cleaning operation can be said to be completely freed from the roving. A residual portion of roving can remain either because the cleaning operation is insufficient or because the time available for cleaning is insufficient.
DE 195 05 225 A1 and the corresponding EP 0 727 380 B1 describes the replacement of roving-bobbin tubes which have been insufficiently cleaned and thus which carry traces of the residue of the roving, by tubes which are free from roving traces.
Along the path between the ring-spinning machine and the roving frame of the empty roving-bobbin tubes, along which such a cleaning system can be provided, it is also known to substitute tubes of one color for another since different color tubes are intended to carry rovings of different types. As a consequence, it is important to ensure that in the replacement of a tube having a trace of roving thereon by a roving-free tube, that the replacement is made by a tube of the same color so that the yarn quality is maintained and there is no interruption in either the bobbin-forming operation or the spinning operation resulting from a switch in the color of the tubes carrying the bobbins.